My b2evolution Version: 2.x

I went to admin and installed openid_plugin-0.5.5 into b2evolution 2.4.5
My plugin setting:
Trust root: *.mydomin.com/
Source for randomness: pseudo
then I activated the plugin...

When I entered my openid url in register form, I got this error:
Fatal error: No XML parser was found in /home/vatanblh/domains/mydomin/public_html/plugins/openid_plugin/php-openid/Auth/Yadis/XML.php on line 366